1. Field of the Invention
This invention generally relates to sealing arrangements for pipe joints and more specifically to an improved clamping device for effecting a seal between a pipe and a manhole.
2. Description of Related Art
Various proposals exist for connecting pipes to manholes in sewer systems. For example, U.S. Pat. No. 3,958,313 for a Method, Apparatus and Product for Improved Pipe-to-Manhole Sealing issued May 25, 1976 to the same assignee as the present invention discloses an underground joint between a sewer pipe and a reinforced concrete manhole riser. A flexible boot slips over the free end of the pipe and an external clamp compresses the seal onto the pipe to produce a boot-to-pipe seal. The other end of the boot penetrates an aperture in a manhole through a normally core-drilled opening in a riser wall. The end of the boot fits in the aperture. A clamping assembly with a clamping band and an integral toggle expander fits inside the boot in alignment with the riser wall. When the toggle expander is operated, it expands the band into the boot and compresses the boot against the riser to produce a boot-to-riser seal.
Occasionally it is necessary to remove the connector from the riser because of improper installation of the seal or an incorrectly sized clamping assembly. In these cases both the clamping band and toggle, that constitute an integral unit, had to be replaced. As disclosed in my U.S. Pat. No. 5,029,907 issued Jul. 9, 1991 for a Band For Effecting A Seal that is assigned to the same assignee as this invention, an integrally formed toggle nests in the end sections of a band and expands the band when a hydraulic jack or other means forces a center vee-shaped portion of the toggle radially outward.
Core drilling through a concrete riser wall produces a porthole of nominal diameter, but occasionally because of core drill outer roundness caused by damage, the actual size will vary from site to site. Optimal sealing must occur over the entire range of variations. It is difficult to achieve optimal sealing with the toggle and clamp of either of the foregoing references if the hole size variations exceed a narrow range.
Another construction of a clamping band for sewer pipe applications utilizes wedge-shaped cam members for acting with followers on a clamping band. As disclosed hereinafter, this approach is more readily accommodates a wider range of hole size variations. Essentially two wedge-shaped members are drawn together by a bolt and nut. The cam members drive follower members, affixed to the band, circumferentially apart. Although this structure has been available for a number of years and provides superior sealing to the toggle structures, it has not been widely accepted, particularly with compression bands for smaller diameter pipes, because the costs of such structures are not justified for smaller diameter pipes. In part this cost reflects a need to maintain an inventory of separate clamping structures for each pipe diameter. Thus, two basic clamping band structures continue to be used and for smaller pipes, optimal sealing force are compromised for reduced costs.